My first run-in with Moqtada al-Sadr's Mahdi army came on March 31 in Baghdad. The US occupation chief Paul Bremer had just sent armed men to shut down the young cleric's newspaper, al-Hawza, on the grounds that articles comparing Bremer to Saddam Hussein incited violence against Americans. Sadr responded by calling for his supporters to protest outside the gates of the Green Zone, demanding al-Hawza's reopening.

I wanted to go, but there was a problem; I had been visiting state factories all day and I wasn't dressed for a crowd of devout Shias. Then again, I reasoned, this was a demonstration in defence of journalistic freedom - could they really object to a journalist in loose trousers? I put on a headscarf and headed over.

Demonstrators had printed up English-language banners that said "Let Journalists Work With No Terror". That sounded good, I thought, and started doing my work. I was soon interrupted, however, by a black-clad member of the Mahdi army: he wanted to talk to my translator about my fashion choices. The situation quickly got serious - another Mahdi soldier grabbed my translator and shoved him against a wall, injuring his back. Meanwhile, an Iraqi friend called to say she was trapped inside the Green Zone and couldn't leave: she had forgotten a headscarf and was afraid of running into a Mahdi patrol.

It was an instructive lesson about who Sadr actually is: not an anti-imperialist liberator, as some have cast him, but someone who wants foreigners out so that he can control large portions of Iraq's population himself. But neither is Sadr the one-dimensional villain painted by the media, a portrayal that has allowed many liberals to stay silent as he is barred from participating in elections and to look the other way as US forces firebomb Sadr City.

The situation requires a more principled position. For instance, Sadr deserves his right to publish a political newspaper - not because he believes in freedom but because we supposedly do. Similarly, Sadr's calls for fair elections and an end to occupation demand our unequivocal support - not because we are blind to the threat Sadr poses but because a belief in self-determination means admitting that the outcome of democracy is not ours to control.

These distinctions are commonly made in Iraq: many people I met in Baghdad condemned the attacks on Sadr as evidence that Washington never intended to bring democracy. They backed Sadr's calls for an end to occupation and immediate elections. But when asked if they would vote for him, most laughed.

Yet in North America and Europe the idea that you can support Sadr's call for fair elections and an end to occupation without endorsing him as Iraq's next prime minister has proved harder to grasp. For arguing this position, I was accused of making "excuses for the theocrats and misogynists" by Nick Cohen, in the Observer, and of being a "socialist-feminist offering swooning support to theocratic fascists" by Christopher Hitchens, in Slate.

All this manly defence of women's rights is enough to make a girl swoon. Yet it's worth remembering how Hitchens rationalised his reputation-destroying support for the war: even if US forces were really after the oil and military bases, he reasoned, the liberation of the Iraqi people would be such a joyous side-effect that progressives everywhere should cheer. With the prospect of liberation still a cruel joke, Hitchens now claims that this anti-woman, anti-gay White House is the Iraqi people's best hope against Sadr's anti-woman, anti-gay fundamentalism. Once again we are supposed to hold our noses and cheer the Bradleys for the greater good, or the lesser evil. There is no question that Iraqis face a mounting threat from religious fanaticism, but US forces won't protect Iraqi women and minorities any more than they have protected Iraqis from torture in Abu Ghraib or bombs in Falluja. Liberation will never be a trickle-down effect of this invasion because domination, not liberation, was always its goal.

The choice in Iraq is not between Sadr's dangerous fundamentalism - echoed by some Sunni groups - and a secular, democratic government made up of trade unionists and feminists. It's between open elections - which risk handing power to fundamentalists but would also allow secular and more progressive religious forces to organise - and rigged elections designed to leave Iraq in the hands of Ayad Allawi and his CIA/Mukhabarat-trained thugs, dependent on Washington for both money and might.

This is why Sadr is being hunted - not because he is a threat to women's rights but because his political demands represent the greatest threat to US control. Even after Grand Ayatollah Ali al-Sistani backed down from his opposition to the handover plans, Sadr continued to oppose the US-drafted constitution, continued to call for the withdrawal of foreign troops and continued to oppose US plans to appoint an interim government rather than hold elections. If Sadr's demands are met and the country left in the hands of the majority, US military bases will be in jeopardy, as will Bremer's privatisation-friendly laws.

Progressives should oppose the attack on Sadr because it is an attack on the possibility of a democratic future. There is another reason to defend his democratic rights: paradoxically, it will help to stem religious fundamentalism's rise.

Sadr has deftly positioned himself not as the narrow voice of strict Shias but as an Iraqi nationalist defending the entire country against foreign invaders. Thus, when he was attacked with the full force of the US military and dared to resist, he earned the respect of millions of Iraqis living under the brutality of occupation.

This shift in attitude is evident in all the polling. A coalition provisional authority poll conducted in May, after the first US siege of Najaf, found that 81% of Iraqi respondents now thought more highly of Sadr. An Iraq Centre for Research and Strategic Studies poll ranked Sadr - a marginal figure six months before - as Iraq's second most influential political player after Sistani.

Most alarming, the attacks appear to be boosting support not only for Sadr personally, but for theocracy generally. In February, the month before Bremer closed down Sadr's newspaper, an Oxford Research International survey found that a majority of Iraqis wanted a secular government; only 21% of respondents said that their favoured political system was "an Islamic state". Fast-forward to August, with Najaf under siege by US forces: the International Republican Institute reported that a staggering 70% of Iraqis wanted Islam and sharia as the basis of the state. The poll didn't differentiate between Sadr's unyielding interpretation of sharia and moderate versions. Yet it's clear that some of the people who told me in March that they supported Sadr but would never vote for him are beginning to change their minds.

I recently received a letter from Major Glen Butler, a US marine helicopter pilot stationed in Najaf. Major Butler defended the siege on the holy city by saying that he and his fellow marines were trying to prevent the "evil" of "radical Muslims" from spreading. Well, it's not working. Helicopter gunships are good at killing people. Beliefs, when under fire, tend to spread.